HotXLS: streaming write and server batch jobs in Delphi

Cet article français présente HotXLS: streaming write and server batch jobs in Delphi pour les équipes qui construisent des solutions avec Delphi, C++Builder, Lazarus/FPC et les composants losLab

L'accent est mis sur les choix pratiques, les pièges et les points de contrôle afin que la solution reste fiable en production

Décisions d'architecture

Treat every workbook as an isolated job. job identifier, output destination, retry policy, timeout, and cancellation behavior / temporary file location, cleanup, quota, and retention for failed workbooks

• job identifier, output destination, retry policy, timeout, and cancellation behavior
• temporary file location, cleanup, quota, and retention for failed workbooks
• batch size, concurrency level, progress reporting, and back-pressure
• which validation can run before final upload or delivery

Parcours d'implémentation

Stream output only after validation checkpoints are defined. The order below keeps the workflow reviewable for Delphi and C++Builder teams.

1. assign a job identifier and output boundary before opening the workbook writer
2. prepare styles, sheets, and headers before streaming row data
3. write rows in batches and checkpoint progress for operators
4. validate size, sheet count, row count, and key formulas before final delivery
5. clean or retain temporary files according to success, cancellation, or failure

Preuves de validation

Batch evidence for operators. Keep these fields with the output or support record.

• job identifier, batch item count, row count, output size, elapsed time, and memory peak
• stage timings for data load, workbook write, validation, save, and upload
• temporary path, cleanup status, retry count, and cancellation reason
• operator-facing failure reason and whether retry is safe

Streaming is a resource policy

Streaming write helps scale workbook generation, but it also limits which parts of the workbook can be revisited later. The job design should decide what must be known before streaming begins.

Notes d'implémentation en production

Traitez HotXLS: streaming write and server batch jobs in Delphi comme un contrat de service explicite autour des appels HotXLS, en séparant validation d'entrée, écriture du classeur, contrôle de sortie et preuves de support

• Définir la source de données, les plages de cellules et le format de sortie avant de créer le classeur
• Consigner le nombre de lignes, les feuilles, les avertissements et le chemin de sortie dans une trace relisible
• Encapsuler les détails applicatifs dans des helpers testables plutôt que dans des événements UI
• Rouvrir ou inspecter le fichier enregistré avant livraison à un autre système ou au client

Défaillances à répéter en test

• Un SaveAs réussi ne prouve pas que le contrat métier est respecté
• Polices, droits et paramètres régionaux peuvent différer entre serveur et poste de développement
• Les journaux ne doivent exposer ni mots de passe, ni données client, ni liens internes

Exemple Delphi détaillé

L'exemple Delphi suivant montre une frontière de service pratique pour ce sujet, avec politiques, journalisation et validation dans une couche testable

procedure RunWorkbookBatch(const Jobs: TArray<TWorkbookJob>);
var
  Job: TWorkbookJob;
  JobResult: TWorkbookJobResult;
begin
  for Job in Jobs do
  begin
    StartJobAudit(Job.Id, Job.OutputFile);
    try
      RequireWritableDestination(Job.OutputFile);
      RequireTempQuota(Job.TempFolder, Job.ExpectedRows);
      JobResult := WriteWorkbookJob(Job);
      ValidateWorkbookForDelivery(JobResult.OutputFile, JobResult.ExpectedRows);
      CompleteJobAudit(Job.Id, JobResult);
    except
      on E: Exception do
      begin
        MarkJobFailed(Job.Id, E.Message, CanRetryWorkbookJob(Job));
        CleanupOrRetainTempFiles(Job, E);
        raise;
      end;
    end;
  end;
end;

function WriteWorkbookJob(const Job: TWorkbookJob): TWorkbookJobResult;
var
  Wb: TXLSXWorkbook;
  Sh: IXLSWorksheet;
begin
  Wb := TXLSXWorkbook.Create;
  try
    Sh := Wb.Sheets[0];
    Sh.Name := 'Batch Output';
    StreamRowsIntoWorksheet(Sh, Job.Reader, Job.Progress);
    WriteBatchMetricsSheet(Wb, Job);
    if Wb.SaveAs(Job.OutputFile) <> 1 then
      RaiseWorkbookSaveError(Job.OutputFile);
    Result := BuildWorkbookJobResult(Job);
  finally
    Wb.Free;
  end;
end;

Liste de mise en production

• Run the workflow on an empty workbook, a normal customer workbook, and a worst-case workbook
• Open the output with the target spreadsheet application or downstream importer
• Log product version, template version, profile, row count, output path, elapsed time, and warning count
• Keep passwords, temporary files, customer data, and support bundles under explicit retention rules
• Add regression workbooks when a customer file exposes a new edge case

Product documentation

HotXLS Component

Exemples de code supplémentaires

procedure TBulkExporter.FillRow(Sender: TObject; SheetIndex, Row, FirstCol,
  LastCol: Integer; var Values: Variant; var Skip: Boolean;
  var Cancel: Boolean);
begin
  if not FReader.Next then
  begin
    Cancel := True;              // data source drained: stop cleanly
    Exit;
  end;
  Values := VarArrayCreate([FirstCol, LastCol], varVariant);
  Values[FirstCol]     := FReader.RecordId;
  Values[FirstCol + 1] := FReader.CustomerName;
  Values[FirstCol + 2] := FReader.Amount;
end;

// fill rows 2..100001, columns A..C, pulling from the reader
Sheet.WriteRows(2, 1, 100001, 3, FillRow);

for FileName in SourceFiles do
begin
  Book := TXLSXWorkbook.Create;        // fresh instance: no state bleed
  try
    Book.StreamingWrite := True;
    if Book.Open(FileName) <> 1 then
      Continue;                        // one bad input must not kill the batch
    Book.SaveAsCSV(ChangeFileExt(FileName, '.csv'), 0, ',');
  finally
    Book.Free;
  end;
end;